Turbocharging a diesel engine?

Discussion in 'Diesel Engines' started by Jonny88, Dec 3, 2010.

  1. DennisRB
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    DennisRB Senior Member

    Yes you can. Turbines produce torque for sure.

    http://www.youtube.com/watch?v=QUkiVcRJuWo

    But that isn't how it works on a normal engine.

    However I do agree with your statement in general. But you were the one talking about "practicality" and in practice when fitting the turbocharger to an engine the engine will see a power increase. The turbo is responsible for that power increase by allowing more air to be combusted.
     
  2. kroberts
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    kroberts Senior Member

    I'm not arguing whether turbine engines can produce power. That is entirely unrelated to the discussion. There is a lot in the device in that video which is not tubocharger.

    The the only way power gets to its intended destination on a turbocharged diesel boat is through the crankshaft. The turbocharger is not storing significant energy or power. It's not producing energy or power. There is no mechanical connection between the turbocharger shaft and the prop or any other device which consumes that power. A turbocharger is an air compressor "head" and nothing more. It depends on the engine for power to do its job, it has no combustion chamber. Any fuel which might still be burning when the exhaust gases leave the combustion chamber of the engine are largely irrelevant.

    There are lots of interesting things that can be done with a turbine. Those things belong on some other thread. The original poster gave parameters for this thread, and IMO only a handful of the posts here had anything at all to do with the OP's intent.
     
  3. Submarine Tom

    Submarine Tom Previous Member

    Sorry RB but your wrong on both counts.

    People kill people.

    -Tom
     
  4. RonL
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    RonL Junior Member

    I for sure don't intend to pick a fight, but I read in the thread starter's only two post, a quest for information and any therory from anyone, the nearest thing to a focal point was large ships.
    I made a couple of comments based on my working engine, I'm a little curious if those are in the group of accusations of misunderstandings, if so, when spring brings a little warmer weather, there might just be some hole drilling, thread tapping and three or four gauges mounted, just to see what takes place and where. Or I might just drag out a book or two.

    I for one find the thread interesting, but have little knowledge of the details, most of what goes on with my engine/turbo operation is in the range of what Easy Rider was asking about. I think if the turbo was removed there would be no detectable difference in how the engine performs. It has seen service of a lite to medium duty work (1987--2011) and still operates.

    In 1990 there was a repair that would make almost anyone cry (I won't go into that) and a wonderful "J-B Weld" story.

    For the record, the engine is 1965 and came with the turbo, according to the spec tag.

    Ron
     
  5. Cheesy
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    Cheesy Senior Member

    I take your point that the engine mentioned it is off topic, however it is probably a good idea to do a little research before you give such a factual opinion on something.

    The turbine wheel of a turbo would be better thought of as an energy recovery device. When the exhaust valve opens on the cylinder gases are still burning and still expanding, these gases are not doing any work and are therefore wasted, that is until you expand them through a turbine. The turbine is not as simple as a propeller in an air stream, it is also a heat recovery device (this has been alluded to by another poster with regard to water cooled vs oil cooled turbos). Now with regard to the loss in efficiency due to 'back pressure' form the turbo in non boost situations, this will be pretty minimal and could be essentially eliminated if you went to the trouble of designing and building a tuned length manifold, infact if you also built a suitable tuned length inlet manifold it is possible that you would have a better volumetric efficiency (in non boost situations) than the original engine without a turbo on it.
     
  6. DennisRB
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    DennisRB Senior Member

    I see. An NRA member. "in my cold dead hands". ;) Didn't you elect to stay out of thread? Maybe you should stick to that until you have some more actual facts of turbocharging to give.
     
  7. Landlubber
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    Landlubber Senior Member

    "I see. An NRA member. "...maybe, maybe not, but it IS the truth......have you ever seen a gun shoot anyone?
     
  8. DennisRB
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    DennisRB Senior Member

    Yeah you are right. It was just an example. I don't feel strongly about gun laws and I don't wish to degrade this discussion to guns. The point is you cant isolate single parts of a system (shooter, gun, bullet) or (turbo, engine, fuel) and say that any one of those parts cant do its job on their own when they operate together to form a system. You must look at the whole system or you are thinking out of context.

    Please I don't want a gun argument! That has the potential to destroy the thread. I have no problems with gun ownership.

    If you want to how some people are completing whole cars including turbocharger systems for under $1300 see my 13 seconds for $1300 challenge. My challenge is to build a whole car up including purchase price of the car that must run the quarter mile in under 14 seconds spending $1300 or less. This is on my car club forum and can be seen below. I am 2JZR31. The cars can be seen in the members car corner in PF street cars. This should give the original poster some idea on turbocharging even though it is for petrol powered cars. Thats not to say a diesel could not enter, but it wouldn't make the desired power. The turbocharging aspect is the same on a petrol or diesel.

    If you are offended my rude language please don't click it.

    http://forums.performanceforums.com/forums/showthread.php?t=67262287
     
  9. kroberts
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    kroberts Senior Member

    Yes. My mother lost her foot because of a gun nobody was near.

    I'm neither pro nor anti-gun in the way of the national debate. Neither side is even close to right in that argument.

    My apologies to the group for bad behavior.

    I somehow thought that a gentleman asking questions about turbocharging his existing diesel was the OP.
     
  10. Submarine Tom

    Submarine Tom Previous Member

    Once again RB, wrong on both counts.
     
  11. Marine Nut
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    Marine Nut Junior Member

    Originally Posted by Marine Nut

    Gentlemen:


    Although this does not really help our original poster and his question, I do believe that it is generally accepted that the BSFC of a turbo charged diesel is better than its non- turbo charged counterpart. In fact, I believe most fuel consumption graphs published by the various manufacturers, and then submitted to the EPA or other air emission entity for emission compliance would also bare this out.

    I don't think the BSFC difference is enormous, but is in the 7-10% range average, meaning that it takes about 7-10% less, fuel to make the same amount of HP hours using turbocharging vs non-turbocharging, all else being equal from an engineering standpoint. Remember, I am not talking power density (that's a given) I am talking BSFC.


    With that said, I do have a question that in the past I have not been able to get a universal answer on. Maybe it will come here?

    So here goes:


    Why, or what exactly is taking place inside the engine to make the engine produce the same HP on less fuel? Really simple question when you think about it, but I am wondering if there is a simple answer.

    Cheers and Happy New Year to All.

    Marine Nut

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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    From : Karl 2

    7-10%, you are correct. There are no current production engines to do this comparison with but I dusted off some old Volvo spec sheets I have:

    MD70C (Naturally aspirated)
    TMD70C (Turbo charged)
    TAMD70C (Turbo Charged and After Cooled)

    All are from the mid 70's.
    BSFC (g/kw/hr) and on the full load curve (Rated rpm the same for all but peak hp is different, comparison is OK for this purpose)

    MD70C: 247 @ WOT, 229 @ 65% of WOT and 240 @ 40%.
    TMD70C: 233 @ WOT, 215 @ 65% of WOT and 240 @ 40%
    TAMD70C: 224 @ WOT, 215 @ 65% of WOT and 239 @ 40%

    "...Why, or what exactly is taking place inside the engine to make the engine produce the same HP on less fuel? Really simple question when you think about it, but I am wondering if there is a simple answer..."

    No, there is not a simple answer and there is, as others have stated, a lot of confusion in this tread as to how Turbo charging works.

    Main reasons (IMO):
    1. Better fill rate and more homogenous charge - More of the fuel injected actually used for combustion.

    2. Less pumping losses (See data above, the Turbo charged engines are not more efficient at the load with little/no boost pressure)

    It really is a matter of recovering the energy released by the fuel. Numbers pulled out of my rear: 35% of the energy in the fuel is used to rotate the crank, 35% is transferred away by the cooling system as heat, 2% is radiated heat, 2% is producing noise and vibrations and the balance escapes via the exhaust. The turbo recovers part of this energy and use it to rotate a turbine.

    Case in point: Two identical engines; one with a wet turbo and one with a dry, heat shielded, turbo. Given that everything else is equal the dry turbo engine will be more efficient. That set-up recovers more of the energy in the exhaust gases instead of getting rid of it via the cooling system.
    Karl2


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    ~~~~~~~~~~~~~~~~~~~~~~~~~~



    Karl 2,

    Thanks for the response. I am sorry, but I think I may have caused a few members to become irritated and will limit my posts in the future closer to the original topic.

    Yes, I can see there are many views and ideas as to why a turboed engine can develop the same output HP and consume less fuel do it.

    One point brought up was related to pressures and loses on the exhaust side balancing that. Many modern high output diesel run boost pressures from 15 to 30+ PSI during normal operation. I think average exhaust pressures under worst case conditions are under 4 PSI (usually under 2 psi?). Seems that the boost side would easily win in this case. To simple of an analogy?

    The discussion later in the thread brought up some input on "power consumer" vs "power producer". An interesting side note to this would be to discuss that knowing that on many large diesel engines (ships mostly?), the turbo shaft is coupled through a complex running clutch and gear reduction system to the engines output, and that this system is actually putting a measurable amount or power into the output on the engine. To me, that could certainly be seen as a "power producer"?

    Thanks again for sharing your thoughts and leaving the politics out. A nice breath of fresh air.

    Marine Nut
     
  12. Karl2
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    Karl2 Junior Member



    Marine Nut,

    Pressure on intake side vs exhaust pressure...Sorry if this sounds "political" but in this context the two has nothing to do with each other. Suggesting that they do (and that it somehow would affect the output or efficency) has its source in a basic misunderstanding regarding how this works.

    A turbo charged engine makes more power and is more efficient - Period. Again, in the context of this post, the relationship between pressure in the intake and exhaust manifold is nothing anybody needs to consider.

    Karl2
     
  13. DennisRB
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    DennisRB Senior Member

  14. powerabout
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    powerabout Senior Member

    I know a guy how raced high performance turbo diesels in offshore race boats and they always had to be carefull with the pressure before the turbo as in a big valved engine it would hold the exhaust valves open and bang!
     

  15. Submarine Tom

    Submarine Tom Previous Member

    The HP Book "Turbochargers" is an excellent read. It is dated, as mentioned, nothing on injected gasoline. It was my Bible when I fabricated my turbo system on a 1600 cc gas, four-stroke, racing engine in the early 80's.

    -Tom
     
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